/*
*class++
* Name:
* StcResourceProfile
* Purpose:
* Correspond to the IVOA STCResourceProfile class.
* Constructor Function:
c astStcResourceProfile
f AST_STCRESOURCEPROFILE
* Description:
* The StcResourceProfile class is a sub-class of Stc used to describe
* the coverage of the datasets contained in some VO resource.
*
* See http://hea-www.harvard.edu/~arots/nvometa/STC.html
* Inheritance:
* The StcResourceProfile class inherits from the Stc class.
* Attributes:
* The StcResourceProfile class does not define any new attributes beyond
* those which are applicable to all Stcs.
* Functions:
c The StcResourceProfile class does not define any new functions beyond those
f The StcResourceProfile class does not define any new routines beyond those
* which are applicable to all Stcs.
* Copyright:
* Copyright (C) 1997-2006 Council for the Central Laboratory of the
* Research Councils
* Licence:
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence as
* published by the Free Software Foundation; either version 2 of
* the Licence, or (at your option) any later version.
*
* This program is distributed in the hope that it will be
* useful,but WITHOUT ANY WARRANTY; without even the implied
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public Licence for more details.
*
* You should have received a copy of the GNU General Public Licence
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street,Fifth Floor, Boston, MA
* 02110-1301, USA
* Authors:
* DSB: David S. Berry (Starlink)
* History:
* 26-NOV-2004 (DSB):
* Original version.
*class--
*/
/* Module Macros. */
/* ============== */
/* Set the name of the class we are implementing. This indicates to
the header files that define class interfaces that they should make
"protected" symbols available. */
#define astCLASS StcResourceProfile
/* Include files. */
/* ============== */
/* Interface definitions. */
/* ---------------------- */
#include "globals.h" /* Thread-safe global data access */
#include "error.h" /* Error reporting facilities */
#include "memory.h" /* Memory allocation facilities */
#include "object.h" /* Base Object class */
#include "stc.h" /* Coordinate stcs (parent class) */
#include "channel.h" /* I/O channels */
#include "region.h" /* Regions within coordinate systems */
#include "stcresourceprofile.h" /* Interface definition for this class */
/* Error code definitions. */
/* ----------------------- */
#include "ast_err.h" /* AST error codes */
/* C header files. */
/* --------------- */
#include
#include
#include
#include
/* Module Variables. */
/* ================= */
/* Address of this static variable is used as a unique identifier for
member of this class. */
static int class_check;
#ifdef THREAD_SAFE
/* Define how to initialise thread-specific globals. */
#define GLOBAL_inits \
globals->Class_Init = 0;
/* Create the function that initialises global data for this module. */
astMAKE_INITGLOBALS(StcResourceProfile)
/* Define macros for accessing each item of thread specific global data. */
#define class_init astGLOBAL(StcResourceProfile,Class_Init)
#define class_vtab astGLOBAL(StcResourceProfile,Class_Vtab)
#include
#else
/* Define the class virtual function table and its initialisation flag
as static variables. */
static AstStcResourceProfileVtab class_vtab; /* Virtual function table */
static int class_init = 0; /* Virtual function table initialised? */
#endif
/* External Interface Function Prototypes. */
/* ======================================= */
/* The following functions have public prototypes only (i.e. no
protected prototypes), so we must provide local prototypes for use
within this module. */
AstStcResourceProfile *astStcResourceProfileId_( void *, int, AstKeyMap **, const char *, ... );
/* Prototypes for Private Member Functions. */
/* ======================================== */
static void Dump( AstObject *, AstChannel *, int * );
/* Member functions. */
/* ================= */
void astInitStcResourceProfileVtab_( AstStcResourceProfileVtab *vtab, const char *name, int *status ) {
/*
*+
* Name:
* astInitStcResourceProfileVtab
* Purpose:
* Initialise a virtual function table for a StcResourceProfile.
* Type:
* Protected function.
* Synopsis:
* #include "stcresourceprofile.h"
* void astInitStcResourceProfileVtab( AstStcResourceProfileVtab *vtab, const char *name )
* Class Membership:
* StcResourceProfile vtab initialiser.
* Description:
* This function initialises the component of a virtual function
* table which is used by the StcResourceProfile class.
* Parameters:
* vtab
* Pointer to the virtual function table. The components used by
* all ancestral classes will be initialised if they have not already
* been initialised.
* name
* Pointer to a constant null-terminated character string which contains
* the name of the class to which the virtual function table belongs (it
* is this pointer value that will subsequently be returned by the Object
* astClass function).
*-
*/
/* Local Variables: */
astDECLARE_GLOBALS /* Pointer to thread-specific global data */
AstMappingVtab *mapping; /* Pointer to Mapping component of Vtab */
AstStcVtab *stc; /* Pointer to Stc component of Vtab */
/* Check the local error status. */
if ( !astOK ) return;
/* Get a pointer to the thread specific global data structure. */
astGET_GLOBALS(NULL);
/* Initialize the component of the virtual function table used by the
parent class. */
astInitStcVtab( (AstStcVtab *) vtab, name );
/* Store a unique "magic" value in the virtual function table. This
will be used (by astIsAStcResourceProfile) to determine if an object belongs
to this class. We can conveniently use the address of the (static)
class_check variable to generate this unique value. */
vtab->id.check = &class_check;
vtab->id.parent = &(((AstStcVtab *) vtab)->id);
/* Initialise member function pointers. */
/* ------------------------------------ */
/* Store pointers to the member functions (implemented here) that provide
virtual methods for this class. */
/* Save the inherited pointers to methods that will be extended, and
replace them with pointers to the new member functions. */
mapping = (AstMappingVtab *) vtab;
stc = (AstStcVtab *) vtab;
/* Store replacement pointers for methods which will be over-ridden by
new member functions implemented here. */
/* Declare the copy constructor, destructor and class dump
functions. */
astSetDump( vtab, Dump, "StcResourceProfile", "Resource coverage" );
/* If we have just initialised the vtab for the current class, indicate
that the vtab is now initialised, and store a pointer to the class
identifier in the base "object" level of the vtab. */
if( vtab == &class_vtab ) {
class_init = 1;
astSetVtabClassIdentifier( vtab, &(vtab->id) );
}
}
/* Functions which access class attributes. */
/* ---------------------------------------- */
/* Implement member functions to access the attributes associated with
this class using the macros defined for this purpose in the
"object.h" file. For a description of each attribute, see the class
interface (in the associated .h file). */
/* Copy constructor. */
/* ----------------- */
/* None */
/* Destructor. */
/* ----------- */
/* None */
/* Dump function. */
/* -------------- */
static void Dump( AstObject *this_object, AstChannel *channel, int *status ) {
/*
* Name:
* Dump
* Purpose:
* Dump function for StcResourceProfile objects.
* Type:
* Private function.
* Synopsis:
* void Dump( AstObject *this, AstChannel *channel, int *status )
* Description:
* This function implements the Dump function which writes out data
* for the StcResourceProfile class to an output Channel.
* Parameters:
* this
* Pointer to the StcResourceProfile whose data are being written.
* channel
* Pointer to the Channel to which the data are being written.
* status
* Pointer to the inherited status variable.
*/
/* Local Variables: */
AstStcResourceProfile *this; /* Pointer to the StcResourceProfile structure */
/* Check the global error status. */
if ( !astOK ) return;
/* Obtain a pointer to the StcResourceProfile structure. */
this = (AstStcResourceProfile *) this_object;
/* Write out values representing the instance variables for the
StcResourceProfile class. Accompany these with appropriate comment strings,
possibly depending on the values being written.*/
/* In the case of attributes, we first use the appropriate (private)
Test... member function to see if they are set. If so, we then use
the (private) Get... function to obtain the value to be written
out.
For attributes which are not set, we use the astGet... method to
obtain the value instead. This will supply a default value
(possibly provided by a derived class which over-rides this method)
which is more useful to a human reader as it corresponds to the
actual default attribute value. Since "set" will be zero, these
values are for information only and will not be read back. */
/* There are no values to write, so return without further action. */
}
/* Standard class functions. */
/* ========================= */
/* Implement the astIsAStcResourceProfile and astCheckStcResourceProfile functions using the macros
defined for this purpose in the "object.h" header file. */
astMAKE_ISA(StcResourceProfile,Stc)
astMAKE_CHECK(StcResourceProfile)
AstStcResourceProfile *astStcResourceProfile_( void *region_void, int ncoords,
AstKeyMap **coords, const char *options, int *status, ...) {
/*
*++
* Name:
c astStcResourceProfile
f AST_STCRESOURCEPROFILE
* Purpose:
* Create a StcResourceProfile.
* Type:
* Public function.
* Synopsis:
c #include "stcresourceprofile.h"
c AstStcResourceProfile *astStcResourceProfile( AstRegion *region,
c int ncoords, AstKeyMap *coords[], const char *options, ... )
f RESULT = AST_STCRESOURCEPROFILE( REGION, NCOORDS, COORDS, OPTIONS, STATUS )
* Class Membership:
* StcResourceProfile constructor.
* Description:
* This function creates a new StcResourceProfile and optionally initialises its
* attributes.
*
* The StcResourceProfile class is a sub-class of Stc used to describe
* the coverage of the datasets contained in some VO resource.
*
* See http://hea-www.harvard.edu/~arots/nvometa/STC.html
* Parameters:
c region
f REGION = INTEGER (Given)
* Pointer to the encapsulated Region.
c ncoords
f NCOORDS = INTEGER (Given)
c The length of the "coords" array. Supply zero if "coords" is NULL.
f The length of the COORDS array. Supply zero if COORDS should be
f ignored.
c coords
f COORDS( NCOORDS ) = INTEGER (Given)
c Pointer to an array holding "ncoords" AstKeyMap pointers (if "ncoords"
f An array holding NCOORDS AstKeyMap pointers (if NCOORDS
* is zero, the supplied value is ignored). Each supplied KeyMap
* describes the contents of a single STC element, and
* should have elements with keys given by constants AST__STCNAME,
* AST__STCVALUE, AST__STCERROR, AST__STCRES, AST__STCSIZE,
* AST__STCPIXSZ. Any of these elements may be omitted, but no other
* elements should be included. If supplied, the AST__STCNAME element
* should be a vector of character string pointers holding the "Name"
* item for each axis in the coordinate system represented by
c "region".
f REGION.
* Any other supplied elements should be scalar elements, each holding
* a pointer to a Region describing the associated item of ancillary
* information (error, resolution, size, pixel size or value). These
* Regions should describe a volume within the coordinate system
c represented by "region".
f represented by REGION.
c options
f OPTIONS = CHARACTER * ( * ) (Given)
c Pointer to a null-terminated string containing an optional
c comma-separated list of attribute assignments to be used for
c initialising the new StcResourceProfile. The syntax used is identical to
c that for the astSet function and may include "printf" format
c specifiers identified by "%" symbols in the normal way.
f A character string containing an optional comma-separated
f list of attribute assignments to be used for initialising the
f new StcResourceProfile. The syntax used is identical to that for the
f AST_SET routine.
c ...
c If the "options" string contains "%" format specifiers, then
c an optional list of additional arguments may follow it in
c order to supply values to be substituted for these
c specifiers. The rules for supplying these are identical to
c those for the astSet function (and for the C "printf"
c function).
f STATUS = INTEGER (Given and Returned)
f The global status.
* Returned Value:
c astStcResourceProfile()
f AST_STCRESOURCEPROFILE = INTEGER
* A pointer to the new StcResourceProfile.
* Notes:
* - A deep copy is taken of the supplied Region. This means that
* any subsequent changes made to the encapsulated Region using the
* supplied pointer will have no effect on the Stc.
* - A null Object pointer (AST__NULL) will be returned if this
c function is invoked with the AST error status set, or if it
f function is invoked with STATUS set to an error value, or if it
* should fail for any reason.
* Status Handling:
* The protected interface to this function includes an extra
* parameter at the end of the parameter list descirbed above. This
* parameter is a pointer to the integer inherited status
* variable: "int *status".
*--
*/
/* Local Variables: */
astDECLARE_GLOBALS /* Pointer to thread-specific global data */
AstRegion *region; /* Pointer to Region structure */
AstStcResourceProfile *new; /* Pointer to new StcResourceProfile */
va_list args; /* Variable argument list */
/* Get a pointer to the thread specific global data structure. */
astGET_GLOBALS(NULL);
/* Check the global status. */
if ( !astOK ) return NULL;
/* Obtain and validate a pointer to the Region structure provided. */
region = astCheckRegion( region_void );
/* Initialise the StcResourceProfile, allocating memory and initialising the
virtual function table as well if necessary. */
new = astInitStcResourceProfile( NULL, sizeof( AstStcResourceProfile ), !class_init,
&class_vtab, "StcResourceProfile", region,
ncoords, coords );
/* If successful, note that the virtual function table has been
initialised. */
if ( astOK ) {
class_init = 1;
/* Obtain the variable argument list and pass it along with the options string
to the astVSet method to initialise the new StcResourceProfile's attributes. */
va_start( args, status );
astVSet( new, options, NULL, args );
va_end( args );
/* If an error occurred, clean up by deleting the new object. */
if ( !astOK ) new = astDelete( new );
}
/* Return a pointer to the new StcResourceProfile. */
return new;
}
AstStcResourceProfile *astStcResourceProfileId_( void *region_void, int ncoords,
AstKeyMap **coords, const char *options, ... ) {
/*
* Name:
* astStcResourceProfileId_
* Purpose:
* Create a StcResourceProfile.
* Type:
* Private function.
* Synopsis:
* #include "stcresourceprofile.h"
* AstStcResourceProfile *astStcResourceProfileId( AstRegion *region,
* int ncoords, AstKeyMap *coords[], const char *options, ... )
* Class Membership:
* StcResourceProfile constructor.
* Description:
* This function implements the external (public) interface to the
* astStcResourceProfile constructor function. It returns an ID value (instead
* of a true C pointer) to external users, and must be provided
* because astStcResourceProfile_ has a variable argument list which cannot be
* encapsulated in a macro (where this conversion would otherwise
* occur).
*
* The variable argument list also prevents this function from
* invoking astStcResourceProfile_ directly, so it must be a re-implementation
* of it in all respects, except for the final conversion of the
* result to an ID value.
* Parameters:
* As for astStcResourceProfile_.
* Returned Value:
* The ID value associated with the new StcResourceProfile.
*/
/* Local Variables: */
astDECLARE_GLOBALS /* Pointer to thread-specific global data */
AstKeyMap **keymaps; /* Pointer to array of KeyMap pointers */
AstRegion *region; /* Pointer to Region structure */
AstStcResourceProfile *new; /* Pointer to new StcResourceProfile */
int icoord; /* Keymap index */
va_list args; /* Variable argument list */
int *status; /* Pointer to inherited status value */
astGET_GLOBALS(NULL); /* Get a pointer to the thread specific global data structure. */
/* Get a pointer to the inherited status value. */
status = astGetStatusPtr;
/* Check the global status. */
if ( !astOK ) return NULL;
/* Obtain a Region pointer from the supplied ID and validate the
pointer to ensure it identifies a valid Region. */
region = astVerifyRegion( astMakePointer( region_void ) );
/* Obtain pointer from the supplied KeyMap ID's and validate the
pointers to ensure it identifies a valid KeyMap. */
keymaps = astMalloc( sizeof( AstKeyMap * )*(size_t) ncoords );
if( keymaps ) {
for( icoord = 0; icoord < ncoords; icoord++ ) {
keymaps[ icoord ] = astVerifyKeyMap( astMakePointer( coords[ icoord ] ) );
}
}
/* Initialise the StcResourceProfile, allocating memory and initialising the
virtual function table as well if necessary. */
new = astInitStcResourceProfile( NULL, sizeof( AstStcResourceProfile ), !class_init,
&class_vtab, "StcResourceProfile", region,
ncoords, keymaps );
/* Free resources. */
keymaps = astFree( keymaps );
/* If successful, note that the virtual function table has been initialised. */
if ( astOK ) {
class_init = 1;
/* Obtain the variable argument list and pass it along with the options string
to the astVSet method to initialise the new StcResourceProfile's attributes. */
va_start( args, options );
astVSet( new, options, NULL, args );
va_end( args );
/* If an error occurred, clean up by deleting the new object. */
if ( !astOK ) new = astDelete( new );
}
/* Return an ID value for the new StcResourceProfile. */
return astMakeId( new );
}
AstStcResourceProfile *astInitStcResourceProfile_( void *mem, size_t size,
int init, AstStcResourceProfileVtab *vtab,
const char *name, AstRegion *region,
int ncoords, AstKeyMap **coords, int *status ) {
/*
*+
* Name:
* astInitStcResourceProfile
* Purpose:
* Initialise a StcResourceProfile.
* Type:
* Protected function.
* Synopsis:
* #include "stcresourceprofile.h"
* AstStcResourceProfile *astInitStcResourceProfile_( void *mem, size_t size,
* int init, AstStcResourceProfileVtab *vtab,
* const char *name, AstRegion *region,
* int ncoords, AstKeyMap **coords )
* Class Membership:
* StcResourceProfile initialiser.
* Description:
* This function is provided for use by class implementations to initialise
* a new StcResourceProfile object. It allocates memory (if necessary) to accommodate
* the StcResourceProfile plus any additional data associated with the derived class.
* It then initialises a StcResourceProfile structure at the start of this memory. If
* the "init" flag is set, it also initialises the contents of a virtual
* function table for a StcResourceProfile at the start of the memory passed via the
* "vtab" parameter.
* Parameters:
* mem
* A pointer to the memory in which the StcResourceProfile is to be initialised.
* This must be of sufficient size to accommodate the StcResourceProfile data
* (sizeof(StcResourceProfile)) plus any data used by the derived class. If a value
* of NULL is given, this function will allocate the memory itself using
* the "size" parameter to determine its size.
* size
* The amount of memory used by the StcResourceProfile (plus derived class data).
* This will be used to allocate memory if a value of NULL is given for
* the "mem" parameter. This value is also stored in the StcResourceProfile
* structure, so a valid value must be supplied even if not required for
* allocating memory.
* init
* A logical flag indicating if the StcResourceProfile's virtual function table is
* to be initialised. If this value is non-zero, the virtual function
* table will be initialised by this function.
* vtab
* Pointer to the start of the virtual function table to be associated
* with the new StcResourceProfile.
* name
* Pointer to a constant null-terminated character string which contains
* the name of the class to which the new object belongs (it is this
* pointer value that will subsequently be returned by the astGetClass
* method).
* region
* A pointer to the Region encapsulated by the StcResourceProfile.
* ncoords
* Number of KeyMap pointers supplied in "coords". Can be zero.
* Ignored if "coords" is NULL.
* coords
* Pointer to an array of "ncoords" KeyMap pointers, or NULL if
* "ncoords" is zero. Each KeyMap defines defines a single
* element, and should have elements with keys given by constants
* AST__STCNAME, AST__STCVALUE, AST__STCERROR, AST__STCRES, AST__STCSIZE,
* AST__STCPIXSZ. These elements hold values for the corresponding
* components of the STC AstroCoords element. Any of these elements may
* be omitted, but no other elements should be included. All supplied
* elements should be vector elements, with vector length less than or
* equal to the number of axes in the supplied Region. The data type of
* all elements should be "double", except for AST__STCNAME which should
* be "character string". If no value is available for a given axis, then
* AST__BAD (or NULL for the AST__STCNAME element) should be stored in
* the vector at the index corresponding to the axis (trailing axes
* can be omitted completely from the KeyMap).
* Returned Value:
* A pointer to the new StcResourceProfile.
* Notes:
* - A null pointer will be returned if this function is invoked with the
* global error status set, or if it should fail for any reason.
*-
*/
/* Local Variables: */
AstStcResourceProfile *new; /* Pointer to new StcResourceProfile */
/* Check the global status. */
if ( !astOK ) return NULL;
/* If necessary, initialise the virtual function table. */
if ( init ) astInitStcResourceProfileVtab( vtab, name );
/* Initialise a Stc structure (the parent class) as the first component
within the StcResourceProfile structure, allocating memory if necessary. */
new = (AstStcResourceProfile *) astInitStc( mem, size, 0, (AstStcVtab *) vtab,
name, region, ncoords, coords );
/* If an error occurred, clean up by deleting the new StcResourceProfile. */
if ( !astOK ) new = astDelete( new );
/* Return a pointer to the new StcResourceProfile. */
return new;
}
AstStcResourceProfile *astLoadStcResourceProfile_( void *mem, size_t size, AstStcResourceProfileVtab *vtab,
const char *name, AstChannel *channel, int *status ) {
/*
*+
* Name:
* astLoadStcResourceProfile
* Purpose:
* Load a StcResourceProfile.
* Type:
* Protected function.
* Synopsis:
* #include "stcresourceprofile.h"
* AstStcResourceProfile *astLoadStcResourceProfile( void *mem, size_t size, AstStcResourceProfileVtab *vtab,
* const char *name, AstChannel *channel )
* Class Membership:
* StcResourceProfile loader.
* Description:
* This function is provided to load a new StcResourceProfile using data read
* from a Channel. It first loads the data used by the parent class
* (which allocates memory if necessary) and then initialises a
* StcResourceProfile structure in this memory, using data read from the input
* Channel.
*
* If the "init" flag is set, it also initialises the contents of a
* virtual function table for a StcResourceProfile at the start of the memory
* passed via the "vtab" parameter.
* Parameters:
* mem
* A pointer to the memory into which the StcResourceProfile is to be
* loaded. This must be of sufficient size to accommodate the
* StcResourceProfile data (sizeof(StcResourceProfile)) plus any data used by derived
* classes. If a value of NULL is given, this function will
* allocate the memory itself using the "size" parameter to
* determine its size.
* size
* The amount of memory used by the StcResourceProfile (plus derived class
* data). This will be used to allocate memory if a value of
* NULL is given for the "mem" parameter. This value is also
* stored in the StcResourceProfile structure, so a valid value must be
* supplied even if not required for allocating memory.
*
* If the "vtab" parameter is NULL, the "size" value is ignored
* and sizeof(AstStcResourceProfile) is used instead.
* vtab
* Pointer to the start of the virtual function table to be
* associated with the new StcResourceProfile. If this is NULL, a pointer
* to the (static) virtual function table for the StcResourceProfile class
* is used instead.
* name
* Pointer to a constant null-terminated character string which
* contains the name of the class to which the new object
* belongs (it is this pointer value that will subsequently be
* returned by the astGetClass method).
*
* If the "vtab" parameter is NULL, the "name" value is ignored
* and a pointer to the string "StcResourceProfile" is used instead.
* Returned Value:
* A pointer to the new StcResourceProfile.
* Notes:
* - A null pointer will be returned if this function is invoked
* with the global error status set, or if it should fail for any
* reason.
*-
*/
/* Local Variables: */
astDECLARE_GLOBALS /* Pointer to thread-specific global data */
AstStcResourceProfile *new; /* Pointer to the new StcResourceProfile */
/* Initialise. */
new = NULL;
/* Check the global error status. */
if ( !astOK ) return new;
/* Get a pointer to the thread specific global data structure. */
astGET_GLOBALS(channel);
/* If a NULL virtual function table has been supplied, then this is
the first loader to be invoked for this StcResourceProfile. In this case the
StcResourceProfile belongs to this class, so supply appropriate values to be
passed to the parent class loader (and its parent, etc.). */
if ( !vtab ) {
size = sizeof( AstStcResourceProfile );
vtab = &class_vtab;
name = "StcResourceProfile";
/* If required, initialise the virtual function table for this class. */
if ( !class_init ) {
astInitStcResourceProfileVtab( vtab, name );
class_init = 1;
}
}
/* Invoke the parent class loader to load data for all the ancestral
classes of the current one, returning a pointer to the resulting
partly-built StcResourceProfile. */
new = astLoadStc( mem, size, (AstStcVtab *) vtab, name, channel );
if ( astOK ) {
/* Read input data. */
/* ================ */
/* Request the input Channel to read all the input data appropriate to
this class into the internal "values list". */
astReadClassData( channel, "StcResourceProfile" );
/* Now read each individual data item from this list and use it to
initialise the appropriate instance variable(s) for this class. */
/* In the case of attributes, we first read the "raw" input value,
supplying the "unset" value as the default. If a "set" value is
obtained, we then use the appropriate (private) Set... member
function to validate and set the value properly. */
/* There are no values to read. */
/* ---------------------------- */
/* If an error occurred, clean up by deleting the new StcResourceProfile. */
if ( !astOK ) new = astDelete( new );
}
/* Return the new StcResourceProfile pointer. */
return new;
}
/* Virtual function interfaces. */
/* ============================ */
/* These provide the external interface to the virtual functions defined by
this class. Each simply checks the global error status and then locates and
executes the appropriate member function, using the function pointer stored
in the object's virtual function table (this pointer is located using the
astMEMBER macro defined in "object.h").
Note that the member function may not be the one defined here, as it may
have been over-ridden by a derived class. However, it should still have the
same interface. */